Toenail ridges are almost always harmless, especially if they run lengthwise from the base of the nail to the tip. Vertical ridges are the most common type and become increasingly normal with age. Horizontal ridges, on the other hand, can signal that your body went through a period of stress or illness. The direction of the ridge is the single most important clue to what’s causing it.
Vertical Ridges: Usually Normal Aging
Vertical ridges run from the cuticle toward the tip of the nail, like tiny parallel lines etched into the surface. They develop because the nail matrix, the tissue at the base of your nail that produces new nail cells, gradually changes as you get older. The nail plate becomes slightly thinner and drier over time, and these lengthwise grooves are the visible result. If you’re over 40 and notice them appearing on multiple toenails without any other symptoms, this is the most likely explanation.
That said, vertical ridges aren’t exclusively an aging thing. A few other conditions can cause or worsen them:
- Dry skin or eczema. Chronic dryness affects the nail just as it affects surrounding skin, producing visible lengthwise lines.
- Underactive thyroid. Hypothyroidism can cause thick, brittle nails with vertical ridges that crumble or break easily. You might also notice puffy fingertips or nails that look more rounded than usual.
- Iron deficiency. Low iron levels can produce vertical ridging along with spoon-shaped nails, where the center of the nail dips inward like a shallow bowl.
- Low calcium. Brittle nails with longitudinal ridging have been linked to low calcium levels.
Horizontal Ridges: A Sign of Disruption
Horizontal ridges are different. They run side to side across the nail, and they form when something temporarily interrupts nail growth at the matrix. The nail essentially “pauses,” leaving a visible dent or groove that slowly grows outward over weeks or months. These are called Beau’s lines, and they act like a timestamp, marking a period when your body was under significant stress.
The list of triggers is wide. Illnesses with high fevers, including pneumonia, measles, mumps, and strep infections, are classic causes. COVID-19 has been identified as a trigger as well. A heart attack or any severe acute illness can leave a horizontal groove behind. Chronic conditions that reduce blood flow to the nail matrix, such as diabetes, peripheral artery disease, and Raynaud’s phenomenon, can also produce them.
Nutritional causes matter here too. Severe zinc deficiency, inadequate protein intake, and the general malnutrition associated with chronic alcoholism can all trigger Beau’s lines. Even major emotional stress, like a death in the family, divorce, or job loss, can disrupt nail growth enough to leave a visible mark.
Because toenails grow slowly (roughly a millimeter per month), a horizontal ridge might not appear until weeks after the event that caused it. If you see one, think back a few months to whether you were sick or going through something physically or emotionally intense.
Trauma From Shoes and Activity
Toenails take a beating that fingernails don’t. Ill-fitting shoes that press on the nail repeatedly can deform the nail over time, and runners, hikers, and anyone spending long hours on their feet are especially prone. If the repeated pressure injures the nail matrix, a ridge or even a split can develop in that nail specifically. This type of ridging typically shows up on one or two toenails rather than all of them, which helps distinguish it from aging or a systemic cause. Switching to properly fitted footwear with enough room in the toe box often prevents further damage, though the existing ridge will need to grow out completely before the nail looks normal again.
Skin Conditions That Affect Nails
Psoriasis and eczema don’t just affect visible patches of skin. Both can target the nail matrix and produce a roughened, ridged nail surface called trachyonychia. In this condition, nails appear opaque and sandpapery with prominent longitudinal ridging. Alopecia areata (an autoimmune condition that causes hair loss) and lichen planus can cause the same pattern.
Nail psoriasis has a few distinguishing features: the nail may lift away from the nail bed at the tip, the surface often has many small pits (sometimes 50 or more on a single nail), and you might notice reddish discoloration around those pits or at the base of the nail. If your ridged toenails are also pitted, discolored, or separating from the nail bed, a skin condition is worth investigating.
How to Tell If Ridges Are Harmless
A few patterns help sort the benign from the worth-investigating. Vertical ridges on multiple toenails, without pain, discoloration, or crumbling, are almost certainly normal. The more of the following features you notice alongside the ridges, the more reason to have them evaluated:
- Ridges that run horizontally across one or more nails, especially if you can’t recall a recent illness or major stressor
- Nails that crumble, split, or break easily, which may point to thyroid dysfunction or a nutritional deficiency
- Spoon-shaped nails (curving inward), a hallmark of iron deficiency
- Color changes, including dark streaks, white bands that run parallel to the base of the nail, or redness around the nail
- Pitting (many small dents in the nail surface), which often accompanies psoriasis
- Ridging on only one nail after an injury, particularly if the nail is also thickened or painful
Smoothing and Caring for Ridged Toenails
If your ridges are cosmetic and not caused by an underlying condition, you can improve the nail’s appearance with a few simple steps. The ridges sit on the surface of the nail plate and can be gently buffed down using a series of nail files. Start with a coarser file to level the ridge, check your progress by running a fingertip across the nail, then follow with a finer file and finish with a buffing file to restore shine. Be gentle. Over-filing thins the nail and can make it more fragile.
Keeping the nail hydrated also helps. The two most effective moisturizing ingredients for nails are urea and lactic acid, both of which increase the nail’s ability to hold water by opening up binding sites in the nail protein. You’ll find them in many foot creams and nail treatments. The catch is that the hydration effect is temporary, so consistent daily application works better than occasional use.
For ridges driven by nutritional gaps, addressing the deficiency resolves the problem over time, though you’ll need to wait for the entire nail to grow out before the improvement is fully visible. Toenails can take 12 to 18 months to replace themselves completely, so patience matters.